Psycho Mantis is an unplayable boss and antagonist from the Metal Gear Solid series and known for his unique boss battle in the classic Metal Gear Solid.

Psycho Mantis is first confronted in Metal Gear Solid (1998) and its remake Metal Gear Solid: Twin Snakes (2004). While he did in those games already, his spirit was revived by Liquid Ocelot in Metal Gear Solid 4: Guns of the Patriots (2008). Psycho Mantis is also one of the main antagonists in Metal Gear Solid V: The Phantom Train (2015), which plays before the Shadow Moses events in MGS (1998).

Psycho Mantis can read and even control the minds of others and uses these abilities in the boss fights. In 1998, he became a popular character due to him being able to “read” the memory cards save files and talk about games like Castlevania: Symphony of the Night to the players.